The present invention relates to a method of removing samples from a bath of killed molten metal, particularly for removing samples from a bath of molten steel for the purpose of ascertaining the aluminum content of steel. The invention also relates to improvements in a device which is utilized for the practice of the method.
It is already known to remove samples from a bath of molten metal by resorting to a vessel which has a destructible cover. The cover disintegrates on immersion of the vessel into the bath of molten metal as a result of heating on contact with molten metal and/or under the pressure of molten metal below the level of the upper surface of the bath. This allows molten metal to penetrate into the interior of the vessel. The withdrawn metal is allowed to set upon lifting of the vessel out of the bath, and the rigid metallic sample is then removed from the vessel for testing.
If a metallic alloy contains one or more ingredients (e.g., aluminum) which exhibit a high affinity to oxygen, it is necessary to subject the alloy to a careful analysis in order to ascertain the extent of the formation of scale which develops as a result of contact between air and the exposed surface of the bath as well as due to contact with air which is adjacent to the surfaces and/or has penetrated into the pores of the fireproof ladle. It has been found that the results of the analysis which is carried out upon samples obtained with resort to presently known methods and/or with resort to presently known sample removing instrumentalities are often highly misleading because the removed samples contain excessive amounts of oxidized ingredients which exhibit a pronounced affinity to oxygen. This is due to the fact that the vessel which is used for removal of samples is likely to entrap and/or otherwise carry along substantial quantities of oxygen in the air which has penetrated into the pores of the material of the vessel as well as air which contacts the exposed surface of the vessel prior to immerson into the bath. Some air is absorbed by the material along the exposed surfaces of the vessel, and additional air is held by the vessel as a result of chemisorption. Such air reacts with aluminum and/or with other readily oxidizable ingredients of the removed sample so that the condition of the sample does not accurately reflect the condition of the major part of the bath of molten metal in the ladle.